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Originally Posted by Mikey980
Money spent on computer models to predict long range temperature cannot predict the climate correctly. Simply turn on your favorite news station and get the 14 day, or even 7 day forecast. Compare it to how accurate it is and you will realize that the weather machine, is too complex for man to understand, at least at this point.
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There is a difference between weather and climate, with weather been short-term and climate been long-term. With climate change we're talking about trying to predict long-term trends, it's not the same as trying to predict local weather patterns over a small number of days or weeks. For instance I might not be able to predict what the weather will be like next week, but I can predict with a very high degree of confidence that summer will be on average warmer than winter.
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Originally Posted by Mikey980
Hundreds of assumptions go into these models, and all it takes is for ONE assumption to be wrong, to mess up the entire model. Also, media attention is only paid to models that would predict drastic changes, such as the world flooding. Conversely, a model that predicts no changes, except the temperature fluctuating and finally returning to normal, will not get published as front page news.
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Hundreds of assumptions go into most models but it doesn't necessarily make the model useless if some of these assumptions turn out to be wrong. If you've ever driven a car, used an electricial appliance, flushed a toilet, flown on a plane or used a computer then the chances are that you are using something that has been designed on a computer using any number of assumptions. Many of these are bound to be "wrong" in the sense that they don't accurately reflect reality but the point is that they are close enough to reality to allow useful models to be constructed.
You also need to think about how sensitive a model is to the assumptions that you make. For instance, if in your climate model you have a parameter for "cow farts" since these produce methane (a known green house gas), you might assume that cows fart on average 10 times a day each. However it could be that they actally fart 20 times a day each. How important this difference is depends on how sensitive the model results are to that particular parameter. If they aren't sensitive then the fact that you used only half the correct number doesn't really matter. If the results are sensitive than you'd be best off going back to the original research and trying to come up with a more accurate figure.